Solvent refining process



sepf`3lof94l- A. L.. sNow *l 2 2,257,283 i SOLVENT REFINING PROCESSFiled 0ST.. 1B., 1937 5 Sheets-Sheet 2 ruw" 'I v1/WMA UVa/7 L. Snow f/ATTORNEY Patented Sept. 30, 1941 SOLVENT REFDIING PROCESS Alvah L. Snow,San Francisco, Calif., assignor to Standard Oil Company of California,San Francisco, Calif., a corporation of Delaware Application October 18,1937, Serial No. 169.687

17 claims.

This invention relates to a process and apparatus for treating complexmixtures of carbon compounds with a selective solvent. Moreparticularly, it involves a process of treating such complex mixtureswith a liquid phase selective solvent at a temperature above theinitial-boiling point, but below the dew point of the mixture beingextracted to effect an efficient separation of the carbon compounds intofractions of diierent chemical types.

As is well known, normally liquid petroleum contains a complex mixtureof hydrocarbons of different types. For example, certain naturalpetroleums are known to contain a minor perlcentage of aromatichydrocarbons and a major proportion of paraflins or naphthenes having5,`

6 and 7 carbon atoms in the naphthene ring. Because of close similarityin properties it has been very diflicult to separate these hydrocarbonsaccording to their chemical types. Liquid phase extraction of petroleumoils with selective solvents at temperatures substantially below theinitial boiling point of the oils constitutes one known method ofrefining petroleum and separating aromatic and/or naphthenichydrocarbons from the remaining oil. Although such va process producesan extract containing relatively more aromatic and more naphthenichydrocarbons and a raffinate relatively more parainic in nature", theseparation is only qualitative and yields fractions containingsubstantial quantities of hydrocarbons which it is desired to eliminatefrom the particular fraction in question.

It is a. well accepted general rule in the art of selective solventrefining that an increase in the temperature of extraction, although itincreases the yield of extract obtained, decreases the selectivity of agiven solvent and yields an extract in which the separation betweenaromatics and/or naphthenes on the one hand and paraflins on the otherhand is less sharp than obtained at lower temperatures. That is, astemperature of extraction is increased, the yield of raffinate islowered and the extract contains more and more of the hydrocarbons whichit is desired to keep in the raflinae. When the temperature ofextraction is lowered, the yield of raffinate increases but it containsan increased amount of theI type of hydrocarbons (e. g. aromatic and/ornaphthenic) which it is desired to retain in the extract. Accordingly ithas heretofore been re garded as necessary to adopt a temperatureintermediate the above mentioned high and low extremes such that a givensolvent will yield a satisfactory quantity of raffinate and yet alsogive a reasonably eiiicient separation or refinement of the petroleumoils.

In the present process selective solvent extrac tion is carried outunder conditions such that the selective solvent is above the initialboiling point but below the dew point of the stock being treated.Remarkable and unpredictable increase in the effectiveness of thelselective solvent extraction process is obtained by this hightemperature operation. The process gives three phases in the extractionzone, namely, a vapor phase raffinate, a liquid phase raffinate, and `aliquid phase extract comprising the` selective solvent with itsdissolved components. Thus a single stock can be separated into threecomponents by a single extraction step.

Accordingly, an object of thednvention is to provide an improved andeffective process and apparatus for treating complex mixtures of carlboncompounds with a selective solvent.

Another object is to' provide a process and apparatus forcountercurrently contacting a normally liquid mixture of carboncompounds with a liquid phase selective solvent having a preferentialsolvent action for one class of the carbon compounds such as aromatics,the temperature of the solvent being above the initial boiling point ofthe mixture and below the dew point thereof under the conditions ofextraction;

A further object is to provide a treating process for continuouslyseparating petroleum into a. plurality of separate'portions comprisingan extract fraction, a lower boiling vapor phase raffinate fraction, anda higher boiling liquid phase raffinate fraction.

Another object is to provide a process of selective solvent extractioncapable of effecting separation o1 a substantially pure component from amixture of carbon compounds having overlapping boiling ranges and arelatively Wide range between the boiling point of the lowest boilingcompound and that of the highest boiling compound of said mixture.

A further object of the invention is to provide a process capable ofseparating substantially pure aromatic hydrocarbons from a petroleumfraction containing parainic compounds having boiling points whichoverlap with those of the arcmatics and also containing paraiinlccompounds having boiling points more than F. higher than the lowestboiling aromatic compound present. y

In the drawings, Figure l is a diagrammatic now sheet illustrating asingle stage treating process embodying the principles of thisinvention. Figure 2 is a diagrammatic illustration of the path ofk flowof the various components through one form of treating column and Figure3 illustrates the path of the solvent and liquid phase stock through asingle plate of such a treating column. Figure 4 is a section on lineIV--IV of Figure 3 and shows an arrangement of bubble caps and bailleplates for producing the flow of the fluids as illustrated in Figures 2and 3. Elgure 5 is a perspective view of a baille plate for theapparatus of Figure 4.

Briefly, the specific embodiment of this invention involves intimatelycontacting a liquid mixture of carbon compounds, such as petroleumhydrocarbons, with a higher boiling selective solvent maintained inliquid phase and at a temperature above the initial boiling point of themixture being treated. In order that there may be a liquid raiiinatephase the solvent should also be at a temperature below the dew point ofthe stock in the treating zone. During the intimate contacting of theselective solvent and the stock being treated the solvent preferentiallydissolves one type of carbon compounds, for instance aromatics, and thissolution is separated to give one of the desired fractions. The morevolatile less soluble compounds such as lower boiling parafnichydrocarbons are converted to vapor phase and separated as such to givea second component from the treating process. The less volatile lesssoluble types of compounds, such as higher boiling paralinichydrocarbons having a boiling point more than 60 F. above that of thelowest boiling dissolved aromatics, form a separate liquid Aphase andcomprise the third component separated from the treating zone.

In the process as illustrated by the flow sheet of Figure l, thepetroleum stock to be treated is passed from storage through valvecontrolled pipe I and heater 2 to treating column 3. The temperature ofthe stock is raised by heater 21 to a point above its initial boilingpoint and preferably below the dew point thereof. Temperatures above thedew point of the stock may be utilized where the temperature of theincoming'solvent is properly controlled so that the mean temperature inthe column is below the dew point of the stock. Since the stock isheated to a temperature above its initial boiling point the mixtureladmitted to the treating column will contain both liquids and gaseswhich are to be intimately contacted with the selective solvent admittedto the treating tower through valve controlled line 4. The temperatureof the entering solvent is controlled by heater 5 or by cooler 6 inrecirculating line 1. The preferred temperature of the solvent is fromthe boiling point of the stock to the dew point ofthe petroleum stockbeing treated. The solvent temperature may be higher than the dew pointof the stock when it is necessary to compensate for low temperatures ofthe stock fed to the column. Likewise, the temperature of the solventmay be lower when the temperature of the incoming stock is higher thanits dew point. In other words, the temperature of the stock and solventshould be correlated so that the temperature in the column is above theinitial boiling point, but below the dew point of the mixture beingextracted and at pressures existing in the column. y

Vapor phase compounds pass upwardly through the treating column and areextracted by the down-owing selective solvent. The vapor phasehydrocarbons pass out the top of the column through line 8, condenser 9and valve controlled conduit III to storage. A portion of the condensedvapors may be returned as reux through pipe I I controlled by valve I2.Liquid phase hydrocarbons may ow either upwardly or downwardly or inboth directions through extraction tower 3. If the selective solvent hasa specific gravity greater than that of the compounds being extracted,then the liquid phase compounds will tend to oat on the selectivesolvent and the direction of ow of the solvent will be predominantlydownward. This is the normal situation, although in some instancesmixtures which have a specific gravity greater than that of theselective solvent being used will be extracted and the direction of flowof the solvent will be predominantly upward. In any event, the liquidphase stock can be separated from the selective solvent and is passedthrough the column in the proper direction. If the stock comprises thetop of the two liquid phase layers then the inlet and outlet ports willhave one posittion; if the stock is on the bottom of the two layers thanthe inlet and outlet ports will have an inverted position. The liquidphase stock which reaches the top of the treating column 3 is removedthrough conduit I3 to separator I4 where any entrained selective solventis allowed to separate from the liquid phase stock. The separatedsolvent is returned to the extraction column through valve controlledline I5 and the separated vstock passed to storage through conduit I 6.

The selective solvent together with its dissolved compounds passes downthrough the tower and is removed from the bottom of the column throughline I1, cooler I8, to separator I9. As previously pointed out, in someinstances liquid phase raflinate hydrocarbons may now to the bottom ofthcolumn and be removed through this same path to the separator I9. Suchliquid phase compounds as are contained in admixture with the selectivesolvent and are separable therefrom will be removed in separator I9 andow through line 20 either by way of valve 2| to the column or by way ofvalve 22 to storage or both as desired.

In the specific illustration given in this specication the petroleumfraction is lighter than the solvent and the direction of ow of thepetroleum stock i`s therefore predominantly upward. However, because theseparation between the two liquid phases is not absolutely complete aportion of the petroleum is carried down the column wtih the solvent byentrainment. The stock may therefore be said to flow both upwardly anddownwardly in the tower. The amount of flow in each direction depends ofcourse on the amountof entrainment. In order to obtain countercurrentextraction it is preferred to have the solvent flow down the tower andthe stock ow up the tower in the oppostie direction. This isaccomplished by removing liquid phase ranate from the top of the toweronly. Stock which is entrained in the solvent then serves merely as akind of reflux inasmuch as it in effect is merely recirculatedVdownwardly from an upper plate to a lower plate from which it.ultimately returns as liquid phase ramnate.

Cooler I8 ln line I'I also serves to reduce the temperature of thesolvent in order to free some of the less soluble compounds which areactually dissolved in the solvent and thereby enable them to bemechanically separated in separator I9 and returned through line 20 andvalve 2| to the treating column as a type of reux. The selective solventtogether with the compounds which remain dissolved therein ls removedfrom the bottom of separator I84 through line 23 to still 2l.

an extracted dissolved compoundsfrom the bottom of treating column 3.The vaporized compounds from heater 26 pass through pipe 21 to thebottom of `treating column 3 `and serve as a source of heat for thetreating tower. Solvent from vaporizer 26 is removed through line 28 tostill 24 where the remaining dissolved compounds are vaporized and passto storage in the manner previously described.

To insure intimate contacting in the extraction `column betweenthemixture being treated and the liquid phase selective solvent, variousmeans may be adopted. A tower filled with suitable packing of refractoryearthenware, glass, etc., comprises one `effective form of apparatus forthis purpose. When such an apparatus is utilized the vapor phaseraiiinate istaken off as overhead and the liquid phase rafiinate isremoved from the bottom of the tower as is also the selective solventwith its extract when the solvent is heavier than the mixture beingtreated. Another `form of apparatus which is adapted for treatment,according to the present invention, is a staged counter-flow in whichaseries of contacting zones for the vapor phase hydrocarbons and liquidphase selective solvent are provided.

After thorough contacting in each of the zones the extract and rafnateare separated and pass to `succeeding contacting zones. It is apparentthat hydrocarbons being extracted should ow in one direction through theseries of contacting zones and the selective solvent in an oppositedirection through the zones.

A column constructed in amanner analogous to an ordinary fractionatingcolumn of the bubble cap type is also an eiicient means of insuringeffective contact between the vapor phase mixture, the liquid phasemixture, and the liquid phaseuextraxgting solvent.

and is as follows:

Solvent is admitted to the column at the top by line 4, passed acrossthe rst bubble plate downwardly through an overflow pipe, back acrossthe second bubble plate in the opposite direction from that in thefirst, through an overflow pipe to the third contacting plate, etc., asshown diagrammatically by the arrows in the solid lines of Figure 2. Thestock being treated is admitted through line I as indicated by thedotted line arrows in this figure of the drawings. Since the stockcomprises a liquid phase portion and a `vapor phase portion these twofractions follow different paths. The vapor phase portion passesupwardly through the bubble caps in the same manner as in anordinaryfractionating column and as shown by the dotted line arrows inthe center of column of Figure 2. The liquid phase stock `flowshorizontally across the plates countercurrently to the selective solventand vertlcally through the pipes outside of the column from `one plateto the other as shown by the dotted line arrows in Figure 2. Extract isremoved from the bottom of the tower through line I1, as shown, andliquid phase raflinate from the top of the tower through line I3. Aportion In such a preferred form of 'apparatus the path of owis shown Y'diagrammatically in Figure 2 of the drawings,

- U-shaped as shown in order of the extract is also removed from thebottom of the tower to a vaporizer and the vapors returned to line 21.

being thoroughly extracted with the selective solvent. l

A form of extraction column especially adapted for use in thepresentprocess is shown in Figures 3 and 4. The column is provided witha series of bubble caps 30 and a series of down-spouts 3|. Oriices 32'in down-spouts 3l plate. The upper end of each of the down-spouts isclosed to prevent entry of the stock being treated which floats on thesolvent layer. Int-he lower end of the down-spout a section is cut outas shown at 33 in order to direct the selective solvent in the generaldirection desired.

Lift conduits 34 and 34 are provided for conveying liquid phase ranatefrom a lower bubble plate to an upper bubble plate. The inlets, that is,the lower ends of the lift conduits, are at the top of the` level atwhich it is desired to keep the liquid phase railinate layer. 'Iheoutlet ends of the lift conduits are preferably below the selectivesolvent level so that the liquid phase raflinate will be intimatelycontacted with `the selective solvent as it rises therethrough.

Two different types of means have been illustrated for causing theliquid phase raiinate to flow upwardly through the lift conduits. Therst is a centrifugal pump 35 and the second a gas lift arrangement 36.When a gas lift is utilized various inert gases may be used. e. g.methane, ethane, propane, a mixture thereof such as obtained inpetroleum refinery gases, nitrogen or steam where condensed water doesnot interfere with the extraction process or render the selectivesolvent useless by reason of dilution. In those cases where Water ismiscible with the solvent and where the selective solvent is relativelynon-selective at the high temperatures used in this process, steam willbe found particularly desirable since the presence of water or watervvapor decreases the miscibility of the solvent and oil. Phenol is anexample of a selective solvent which is relatively non-selective at hightemperatures and which can be rendered more selective by the addition ofwater by this or other methods. Another gas which may be utilized in thegas lift'comprises the raffinate vapors themselves which may be removedfrom the top of the extraction tower. compressed and introduced into thegas lift device.

Pipe 31 controlled by valve 38 is provided for introducing the liftinggas into the liquid in lift conduit 34. The bottom end of conduit 34 isthat the liquid phase raffinate will flow into level above the gasinlet.. The upper end of conduit 34 comprises a goose-neck portion whichserves simultaneously as a. gas trap and siphonbreaker. The lifting gasaccumulates in the top of the U and is removed through line 40 in orderto prevent formation of a gaspocket. Also line 40 acts as a breather toprevent siphoning of fluid from the upper plate through inlet 4|downwardly to the lower plate. l

The level of the solvent and liquid raffinate phase relative to thevarious inlet and outlet conduits is illustrated at of Figure 4. Thelower layer `as represented in this ligure is selective solvent and theupper layer of liquid is the rafllnate being extracted.

Vapor phase rainatepasses from the top` of the tower through lineltiafter serve to admit? selective solvent to the l down-spoutthrol-Igl'fl` which the solvent passes to the next lower bubble the Uand have an upperV the bottom bubble plate Figure 3 shows thearrangement of parts and path of liquid flow on a single bubble plate.Three bubble caps 30 are provided and are separated by a bafiie platehaving a cylindrical portion 44 surrounding the center bubble cap andwing portions 45 extending from the cylindrical portion to the sides ofthe column. Slots 41 (see Figure 5) are provided in the top edge of thebaille to direct the upper liquid phase through the desired path offlow. Likewise, slots 48 are placed in the bottom edge of the baffle tocause the selective solvent to flow around the several bubble caps asshown by the solid line arrows of Figure 3. Specifically, the selectivesolvent fiows from overflow pipe 3Ial around and under the first bubblecap (top of Figure 3) through slot 48 into the cylindrical portion ofthe baffle around-the center bubble cap and out through the second ofslots 48 around and under the third bubble cap to outlet overflow pipeSIb. As indicated by the dotted line arrows the upper layer liquid phaserafnate flows countercurrent- 1y to the selective solvent and passesfrom inlet pipe 4l over and around the lower' bubble cap through slot 4lacross the center bubble cap out second slot 41 and around the thirdbubble cap to outlet conduit 42. The wings 45 and higher portions 46 'ofthe baille plate serve to prevent the liquid phase rafiinate fromflowing directly across the bubble plate from inlet to outlet. The vaporphase rafnate passing through the bubble caps is extracted by the lowersolvent layer and simultaneously the vapors act as an efficient meansfor agitating the two liquid phases passing across the bubble plate.Thus intimate contact between all three phases is effected in a simpleand efficient manner.

The eiiiciency of separation of the two liquid phases on each ofthebubble plates is subject to control by design of the'size of the column,gas rates through the bubble caps, rate of flow of the liquid phases,etc. However, it should be noted that perfect separation is notabsolutely essential since entrainment of either solvent in the stock orstock in the solvent, or both, merely acts as a reflux in that it feedsback a portion of the liquid entrained to the bubble plate from which itcame. This entrainment of course decreases the ne't rate of flow throughthe treating zone, but up to a certain degree may be found to increasethe efficiency of extraction as is the case with any reflux.

In its broad aspects the present invention isI applicable to a greatnumber of mixtures of chemical compounds which are difficult to separatebecause of similarity of boiling points, solu` bility characteristics,or because of formation of constant boiling mixtures. For example, theselective solvent extraction process may be applied to' mixtures ofcompounds such as phenols, aromatics, sulfur compounds, olefines,naphthenes It will be necessary of course to provide at least oneextraction zone for each three components or groups of components to beseparated. However, the process at present is regarded as having itsgreatest utility for the extraction of substantially pure aromatichydrocarbons from extremely complex mixtures of aromatics, naphthenes orparaffins which occur in natural gasolines of relatively Wide boilingrange such as 360 F. end point distillates.

Repeated reference has been made throughout this specification to theuse of selective solvents in the process. This generic term is used todefine a solvent which has greater solvent power for at least onecomponent of a multi component system than it has for other componentsof that system. Stated conversely, the term selective solvent designatesa solvent which has less tendency to dissolve one compoand paraflins,which commonly occur in petroleum distillates. These mixtures can bepassed through a single extraction zone or a series of extraction zonesunder conditions of temperature and pressure such that the mixture isseparated into different components, one component or group ofcomponents being removed from the bottom of each extraction zone as anextract phase, the more volatile component or group of components beingremoved from the top of the extraction zone as a vapor phase overheadand the less volatile less soluble component or group of componentsbeing removed from the top of the extraction zone as a liquid phaserainate.

nent of a mixture than other components thereof. The greater thedifferential in solvent power of a selective solvent for differentcomponents of the mixture, the greater is its selectivity and the moreefficient it will be in the extraction of the component for which it hasthe greatest solvent power.

A selective solvent useful for the present process should be highlyselective and should have a boiling point well above the dew point ofthe stock to be treated. The selective solvent must also be ofincomplete miscibility with the stock being treated -at the temperatureof extraction. In other words, the suitability of a known selectivesolvent for the process of this invention can be primarily determined bytwo physical characteristics, namely, boiling point and miscibilitytemperature. Since the process is operated at temperatures above theinitial boiling point of the stock, but below its dew point, thetemperature of complete miscibility of solvent and stock must be abovethe dew point of the stock under the conditions of extraction. Thisproperty can be readily ascertained by a simple miscibility test atelevated temperature. It should of course be recognized that by theterms dew point and boiling point used above, one means the dew point orboiling point in the presence of the selective solvents and under theconditions of extraction. For example, vacuum may be utilized on theextraction tower and thereby permit use of a selective solvent whichwould be miscible with thestock being treated at its ordinary initialboiling point, but which is of incomplete miscibility with the stock atthe initial boiling point of the stock and the dew point of the stockunder the conditions of extraction, namely, high vacuum. The use ofvacuum is therefore contemplated as falling within the broad scope ofthe present invention.

The following compounds are illustrative of high boiling selectivesolvents which have high temperatures of miscibility with most petroleumstocks and which are therefore 'operative for separating aromatics suchas benzene or toluene from natural petroleum distillates containing thesame: triethylene glycol, diethylene glycol, acetamide, monoacetin,diethanolamine, diaminopropanol. In general polar compounds selectedfrom the group consisting of hydroxy benzenes, amides, chlorinatedhydrocarbons and esters of polycarboxylic acids which have boilingpoints and solubility characteristics such as above discussed arecontemplated as falling within the broad scope of the invention. Thesolvents selected from this group preferably should have a `the stock.'I'he entire `tion with the usual normally liquid petroleum `fractions.

Those selective solvants whicnfare misclble withthe mixture of compoundsbeing extracted `can be utilized in some instances `by adding Vto thesolvent a diluent which is miscible with the solvent, but immisciblewith` Ithe` stockr being` treated.` For-example, inthe treatment ofvery,V

volatile stocks, phenol` may have a suitable boil` ing point, but have amiscibility temperature below the dew point of thestock. In suchinstances `the phenol may be diluted withwater to render it operative inthe` process of this invention.

Other diluents which are characteristically im- `miscible withhydrocarbons orpetroleum fractions and which are often miscibflewith thesolvents are carbon compounds having a largenumber of hydroxy groups.Glycerol is an example of a poly-hydroxy alcohol having high miscibilityl temperatures with petroleum fractions and which is operative as a`diluentin the above suggested combinations.

Obviously, specific conditions of, operation such I as temperature,pressure, relative solvent to stock volumes, and proportion ofvaporlphase railinate to liquid phase railinate will vary with theparticular mixture being treated and with the selective solvent used. Aspreviously pointed out, a

critical feature of the invention comprises operation oi' the process ata temperature above the initial boiling point, but below the dew pointof t process "will usually be carried `out at atmospheric pressures,`although atmospheric desirable in tional jcost pressures will be foundsunlclently some instances to justify the addioccasioned by` operationunder vac- It will be observed that the present `process isfundamentally diierent from ordinary selective solvent extractionprocesses in that it operates at temperatures above the boiling point ofthe l stockbeing treated. Theprocess is also fundamentally differentfrom" ordinary distillation processes in that three phases are presentancil three` components are from the treating zone.

'I'he following principal advantages oi' the invention will be readilyapparent. Mixtures of paraliins, aromatica, etc. having much widerboiling `ranges can be separated chemical types by the process o1' thisinvention. Heretofore it has been 'possible to separate` pure aromaticsfrom parafllns by treatment of relatively narrow fractions in a largenumber of carei'ully controlled fractionating steps. The presentinvention avoids such complexmulti-stage operations. By utilizing thepresent process it is unnecessary `to operate ai; temperatures above theend point of the stock since the high boiling, less soluble components,e. g., paraiiins, are not vaporized as isthe case with ordinarydistillation processes carried out in the presence of a solvent. Byoperating at these lowertemperatures the eftlciency of extraction oi.'the more soluble components, e. g. aromatics, is increased since thereis less tendency to distil them outof the solvent.

-The process herein` described effectively separatesthe less solubleparalnic compounds having boiling points nearest those of thearornatics.` Normally-these very similar components are the mostdinicult to separate and cause the greatest `super-atmospheric pressuresmaybe used. Subsaid treating difliculties inf distillation operations.After treatment by the present process any paraflinlc constituents whichhappen toremain dissolved in the extract with the aromatics are found tohave a boiling point; suiii'ciently different from the aromatics (asmuch as 60 F. or more)` that they can readily be removed by ordinarydistillation andfractionation after separation from the solvent.

The actual distillation operation is more eilicient by reason of thefa'ct that the parallins remain in a separate liquid phase than is thecase 'Where theparailins are dissolved in a solvent. This is believed toresult from the -fact that a,

greater diierentlal in boiling points is produced by the selective`solvent when only one compol nent is dissolved in the solvent than whenthe entire mixture lsdis'solved therein. I'his greater differential inboiling points in turn increases the eiliciency `of `separation by thefractionation process. Other numerous advantages will be apparent tothose skilled in the art.

While the character of this invention has been described in detail thishas been done by way of t illustration `only 'and with the intention`that no limitation should be imposed `upon theinvention thereby.Likewise,the drawings are to be regarded as diagrammatical, no attempthaving been made to show all the necessary details such as pumps,valves, `pressure control devices and the like. It will be apparent tothose skilled in the art that numerous `modincations and variations maybe adopted in the apparatus and method of the invention which is ofthescope of the appended claims. i

I claim: l. A process oi. separating a multi-component mixture of`carbon compounds into more than two components which comprisespassingsaid mixture through a treating zone, passing through jzone a selectivesolvent which remains in liquid phase and is of incomplete miscibilitywith said mixture, converting a portion only of said multi-componentmixture to vapor phase whereby the solvent phase, a vapor phaseraiiinate and a liquid phase raiilnate are simulsimultaneously separatedtaneously present in said zone, passing said vapor phase componentsthrough said treating zone, intimately `contacting said three phaseswhile passing said liquid phase raillnate in a direction Xopposite tothat of said liquid solvent phase to according to selectively dissolveone type of carbon compound in said solvent, removing the treated vaporphase, and separating the two liquid phases to obtain fractions fromsaid treating zone.

2. A process of separating aromatic hydrocarbcns from mixturescontaining aromatic and non-aromatic carboncompounds jof similar boilingrange which comprises passingsaid mixture through a treating zone,passing through said `treating zone a liquid phase selective solvent forsaid aromatic compounds, which solvent is of incomplete miscibility withsaid mixture, cont verting a portion only of the mixture oi carboncompounds to vapor phase whereby a solvent phase, a vapor phaseraillnate and a liquid phase ramnate are simultaneously present in saidzone, passing said vapor phase components -through said treating zone..intimately contacting said three phases and passing said liquid phaserailinate countercurrently to said solvent phase to selectively dissolvearomatic compounds in `said solvent. and separately removing the vaporphase,

phase selective solvent which is of incompletef miscibility with saidmixtureat the dew point thereof, maintaining the temperature in lthetreating zone abovey the initial boiling .point but belowv the dew pointofthe mixture under the conditionsofextraction whereby a vapor phaseraffinate, a liquid phase raffinate and a liquid phase extract aresimultaneously presentrin said zone, intimately contacting the saidthree phases whileflowing said liquid phase rainate throughsaid-treating zone in one direction and flowing said liquid phaseextract through said treating zonein the opposite. direction, andseparately removing the treatedvapor phase, the liquid raffinate 'phaseand the liquid extract phase from thetreating zone. l f

4. A process of separating. aromaticY hydro--Y carbons from petroleumdistillates which comprises extracting said distillate withv a liquidphase vselective solvent at a temperature above thev initial boilingpoint but below the dew point of said distillate and under suchconditions of extraction that a vapor phase raffinate, a liquid phaseraflinate, and a liquid phase extractare f simultaneously present, saidselective solvent being in liquid phase andA of incomplete miscibilitywith the distillate at the temperature of extraction, passing saidliquid phase raiiinate countercurrently with respect to said liquidphaseextract; andl separating three different phases comprising-avaporphaserafiinate, a liquid phase raffinate and a liquid phaseextract. Y

5. A process as defined in claim 4, in which the selective solvent is anhydroxyether having a boiling point above approximately 300 F.

'6; A process asin claim 4, in which the selective solvent is apoly-ethylene glycol.

'7. A' process of treating a normally liquid petroleum fractioncontaining hydrocarbons of dew point thereof into said fractionatingvcolumn at av point above that at which said mixture is admitted,vmaintaining the'temperature in said columnvabove th'e'initialboilingpoint but belowv the dew point of said mixture and under suchconditions that a vapor phase raffinate, a liquid phasefraihnate, and aliquid phase extract are simultaneously present, passing said liquidphase v,raffinate counter/currently to said liquid phase extract, andycontinuously removing vapor phase raiiinate and liquid phase raiiinatefrom the top of said column and continuously removing liquid phaseextract from the lower portion of said fractionating column.

9. A process as dened'in claim 8, further .characterized inthatentrained railinate is separated from the liquid phase extract andreturned to the fractionating column. 10. A process as defined in claim8, further characterized in that entrained selective solvent isseparated from the liquid phase raftiinate and returned to thefractionating column.

l1. A process of treating a multi-phase mixture of carbon compoundshaving more than one liquid phase which comprises, forming a multiphasesystem having heavier and lighter liquid phases by onlypartiallydissolving said mixture in a selective solvent, separating saidliquid phases into a lighter and a heavier portion, passing the lighterportion through an extraction system in onedirection', passing theheavier portion through said extraction system in a different direction,partially vaporizing undissolved carbon compounds of said mixturewithout substantial vaporization of said solvent and contacting thevapors with at least one of said liquid phases different from saidpartially vaporized undissolved liquid phase.

l2. A process of separating according to chemical type a multi-componentmixture of carbon compounds which comprises passing said mixture througha selective solvent extraction zone, forming an undissolved vapor phasefraction and an the aromatic and parainic types and in which the boilingpoint ofthe highest boiling paraflinic hydrocarbon is more thanapproximately 60 F. above'the boiling point of the lowestboilingaromatic vhydrocarbon contained therein, which comprisesv passingsaid `normally -liquid petroleum fraction throughl a treating zone,passing through said treatingzone a liquidphase selectivesolvent whichis of incomplete miscibility with theA petroleum fraction-at the'dewpoint thereof,

maintaining the temperature `in the treating zonev above the initialboiling point but below the dew point'of 'the fraction undertheconditions ,of extraction whereby. a vapor phase raffinate, a liquidphase raffinate and a liquid'phase extract are simultaneously present inthe zone, intimately' contacting said three phases,lpassing` said liquidphase rafiinatecountercurrently to said liquid"l phase.l extract,. andseparately removing the ducing saidmixture intofa 'frictionating column.ata point intermediate the ends thereof, c'bntinu---A ously introducinga high boiling selective solventk of incomplete miscibility with themixture at the undissolved liquid phase fraction in said zone, passingsaid undissolved fractions in-said zone countercurrently to a liquidphase selective solvent having a boiling9 point substantially above theendpoint of said mixture of carbon compounds, contacting saidundissolved phases with said selective solvent, withdrawing a liquidphase selective solvent extract from said extraction zone at one point,withdrawing a liquid phase radinate from said extraction zone at asecond point remote from said rs't point, maintaining the temperature insaid zone at said second point below thedew point but above the initialboiling point of said mixture of carbon compounds, and maintaining saidselective solvent incompletely miscible with said mixture of carboncompounds substantially throughout the extraction zone.

y 13. A process of separating according to chemical type amulti-component mixture of carbon compounds which'A comprises passingsaid mixture through a selective solvent extraction zone, forming anundissolved vapor phase fraction and an undissolved liquid phaserfraction in said zone, passing` said undissolved fractions in said zonecountercurr'entlya to a liquid phase selective solvent having a oilingpoint substantially above the end point of said mixture of. carboncompounds, contacting said undissolved phases with said selectivesolvent, withdrawing a liquid phase selective solvent extract from saidextraction zone at onepoint, withdrawing a liquidphase railinate fromsaid extraction zone lat a second point remotefrom said rst point,maintaining the temperature in said zone at said second point below thedew point but above the initial boiling point of said mixture of carboncompounds, and maintaining said selective solvent incompletely misciblewith said mixture of carbon compounds substantially throughout theextraction zone byadding to `said solvent a diluent immiscible with saidmixl lective solvent having a boiling point substantially above the endpoint of said mixture of carbon compounds, contacting `said undissolvedphases with said selective solvent, withdrawing a liquid phase selectivesolvent extract from said extraction zone at one point, withdrawing aliquid phase rainate from said extraction zone at a second point remotefrom said first point, maintaining 1 the temperature in said zone atsaid second point low the dew point but above the initial boiling pointof said mixture of carbon compounds, and

maintaining said selective solvent incompletely i miscible with saidmixture of carbon compounds substantially throughout the extractionzone.

15. A process as defined in claim 14 in which the selective solvent isan hydroxy ether having a boiling point above approximately 300 F.

416. A process f separatingaccording to chemical type a multi-componentmixture of carbon compounds which comprises passing said mixture througha selective solvent extraction zone, forming an undissolved vapor phasefraction and an undissolved liquid phase fraction in said zone, passingsaid undissolved fractions in said zone countercurrently to a liquidphase selective solvent comprising a liquid phase hydroxy benzene havinga boiling point substantially above the end point of said mixture ofsaid carbon compounds,

contacting said undissolved phases with said selective solvent,withdrawing the liquid phase hydroxy benzene together with its dissolvedcarbon compounds from said zone at one point, withdrawing a liquid phaseraffinate from said extraction zone at a second point remote from saidfirst point, maintaining the temperature in said zone at said secondpoint below` the dew point but above the initial boiling point of saidmixture of carbon compounds, and maintaining said selec-` tive solventincompletely miscible with said mixture of carbon compoundssubstantially throughout the extraction zone.

1'?. A process of separating according to chemical type amulti-component mixture of carbon compounds which comprises passing saidmixture through a selective solvent extraction zone, forming anundissolved vapor phase fraction and an undissolved liquid phasefraction in said zone, passing said undissolved fractions in said zonevcountercurrently to a liquid phase selective solvent comprising aliquid phase ester of a polycarboxylic acid having a boiling pointsubstantially above the end point of said mixture of said carboncompounds, contacting said undissolved phases with said selectivesolvent, withdrawing the liquid phase ester of a polycarboxylic acidtogether `with its dissolved carbon compounds from said zone at onepoint, withdrawing a liquid phase raiiinate from said extraction zone ata second point remote from said first point, maintaining the temperaturein s aid zone at said second point below the dew point butabove theinitial boiling point of said mixture of carbon compounds, andmaintaining said selective solvent incompletely miscible with saidmixture of carbon compounds substantially throughout the extractionzone. ALVAH L. SNOW.

